1. Field of the Invention
The present invention relates to an evaporative fuel treatment device for absorbing evaporative fuel from a fuel tank of a vehicle and to prevent the evaporative fuel from being released to the atmosphere.
2. Description of Related Art
Conventionally, it has been well-known that the evaporation amount of evaporative fuel from fuel systems such as a fuel tank and a carburetor increases with the increase of temperature. Immediately after a vehicle stops, the temperature inside the fuel tank is especially high due to active evaporation of the fuel, which requires an evaporative fuel treatment device having a function to accumulate the evaporative fuel temporarily.
An evaporative fuel treatment device including an evaporative fuel absorber filled with activated charcoal disposed between the fuel tank and the intake pipe connected to the engine has been widely known and accumulates the evaporative fuel temporarily by the evaporative fuel absorber when the engine stop. The evaporative fuel treatment device takes in the air from the outside of the evaporative fuel absorber, and the evaporative fuel caught by the activated charcoal is purged to purify the activated charcoal by absorbing the evaporative fuel into the intake pipe side. The evaporative fuel absorber is equipped with an electromagnetic valve to connect or interrupt the connection between the inside and the outside of the evaporative fuel absorber. The electromagnetic valve is normally open, but is closed to accumulate negative pressure therein when leakage is checked in the evaporation system. Leakage of the evaporative fuel is judged by monitoring the negative pressure value.
As one of such evaporative fuel treatment devices, an evaporative fuel gas diffusion prevention device disclosed in JP-A-6-159160 has been proposed.
However, according to the above-described conventional evaporative fuel treatment device, since a hose is used to connect the electromagnetic valve and the evaporative fuel absorber, there is a problem in that absorbed evaporative fuel is apt to leak from the hose. An evaporative fuel absorber connected directly to the electromagnetic valve is also known, where one end of the electromagnetic valve is inserted into a case of the evaporative fuel absorber and a fixing stay of the electromagnetic valve is screwed to the case of the evaporative fuel absorber with bolts or the like. However, when an external pressure is applied to the electromagnetic valve in this evaporative fuel absorber, the electromagnetic valve is shifted from a predetermined position, which may cause leakage of the evaporative fuel from the portion connecting the evaporative fuel absorber to the electromagnetic valve.
When the air is supplied to the evaporative fuel absorber after being filtrated by a filter disposed inside the electromagnetic valve, dust from the outside may clog up the filter. Furthermore, water entering the electromagnetic valve from the outside may rust the valve body, which causes malfunction of the electromagnetic valve, or may clog up the filter.